Originally posted by Blizz: I think the positive anomalies for Australia for May could well challenge April 2005. Blair would know more.

The last time we checked last week the mean temperature anomaly for May (+3.3) was running about 0.7 ahead of April 2005, although you'd expect that to settle back a bit over the second half of the month. Definitely looks an extreme month though.

Looks like the alps (mostly Vic) are going to get there first fall for the season in the coming hours.

Hotham has been hovering around 0º for most of today with showers falling. So when the colder arrives in the following hours, there shouldn't be much of a proble to get 5-10cm providing the moisture doesn't dry up too much post-frontal.

The WZ GFS snow forecast is going for 10 to 20cm overnight. I'd be surprised if there's anything in it for the CT or BMs, though a few flakes around Shooters might be possible, as Blizz said. Latest LAPS and mesoLAPS have moved the colder air a bit southwards, with the 540 line only up to around Cooma. But the timing is good, with the coldest air moving throuh around daybreak.

_________________________Caution: Any items linked to in this post may change and become irrelevant or expire over time. Use good meteorological practice and ALWAYS check date and time on charts before using them.

Originally posted by pete25: Hey Habs can you please explain to me what the "540 line" is and how it affects the colder weather pattern for Victoria?

From the WZ glossary:

Quote:

Thickness Thickness usually refers to the depth of the 1000-500 hPa layer in the atmosphere. However charts are also produced for thicknesses of other layers in the atmosphere as well. The thickness gives an indication of the mean temperature within a layer; lower thicknesses indicate colder air, higher thicknesses warmer air.

Forecast MSL charts will also often show the 1000-500 hPa thickness as dashed lines. The thickness on these charts is usually given in decametres. So the 540 line indicates the 1000-500 hPa layer is 5400 metres deep.

Thickness charts in general and the 1000-500 hPa thinkness charts in particular are also very useful for determining baroclinic zones and development. Thickness lines can also indicate the steering direction of surface highs and lows.

Pretty much the '540' over a region is the first sign of a possible cold spell. So when you begin to see thickness in the sub 540 area, you're a good chance, providing that moisture and triggers are there, of getting a few flakes.

That's why the 540 line is blue on the WZ model charts More boringly, the 576 line, which is red, suggests heatwave weather in southern AUS. The 520 line is drawn in purple, but only the Taswegians and Kiwis get to see much of it.

_________________________Caution: Any items linked to in this post may change and become irrelevant or expire over time. Use good meteorological practice and ALWAYS check date and time on charts before using them.

SnowMac, thanks for posting up those old SA snow pics!! I'd love to see something like that this winter here.... Last time anything like that was really August 1996... when I was lucky to be at Lobethal in the Adelaide Hills..

Interesting little observation on the train this morning: All through the flood plains of the Nepean around Emu Plains and Penrtih (as seen from the train) there was a substantial frost, however Penrith AWS (located out in the lakes development) recorded a minimum of 4.4ºC.

Actually, we're looking down the barrel of getting further into the year without a sub-zero minimum than any of the previous years on record (50) at the post office. It's a tad academic - we've been down to 0.1° there and it was -1° here at home that night but interesting all the same. Tonight's probably our last chance before May 31 but I can't see it being colder than last night (0.2°).

Last year we'd been below -5° by this point.

Here are the dates of the first sub-zero minimum each year previously.

Code:

1957 15 April
1958 21 May
1959 10 May
1960 25 April
1961 08 May
1962 28 April
1963 05 April
1964 12 April
1965 22 March
1966 10 April
1967 15 May
1968 15 May
1969 24 April
1970 29 April
1971 01 May
1972 26 April
1973 09 May
1974 21 May
1975 03 April
1976 23 April
1977 10 April
1978 27 April
1979 12 April
1980 28 April
1981 29 April
1982 30 April
1983 18 April
1984 26 April
1985 20 April
1986 28 April
1987 11 April
1988 12 May
1989 25 May
1990 19 May
1991 22 April
1992 19 May
1993 20 April
1994 07 May
1995 03 April
1996 09 April
1997 08 April
1998 14 April
1999 22 April
2000 22 April
2001 13 April
2002 08 May
2003 31 May <--
2004 26 April
2005 30 April
2006 03 April
2007 -

I don't think there's anything too untoward about it. As you say there's been less really stable weather and there's been more moisture about with the H-belt struggling to find its way north. I would like to have seen a bit more in the rainfall column as a result but what can you do.

Just under 2.5° here now. The beer's out the back and the Wobblies have got work to do!